Significant advances in the treatment of depression have been made in the past decade. Since the introduction of selective serotonin reuptake inhibitors (SSRIs), i.e., Prozac®, many patients have been effectively treated with anti-depressant medication. New medications to treat depression are introduced almost every year, and research in this area is ongoing. However, an estimated 10 to 30 percent of depressed patients taking an anti-depressant are partially or totally resistant to the treatment. Those who suffer from treatment-resistant depression have almost no alternatives. Thus, there is a need to develop alternative treatments for these patients.
The use of electrical stimulation for treating neurological disease, including such disorders as movement disorders including Parkinson's disease, essential tremor, dystonia, and chronic pain, has been widely discussed in the literature. It has been recognized that electrical stimulation holds significant advantages over lesioning since lesioning destroys the nervous system tissue. In many instances, the preferred effect is to modulate neuronal activity. Electrical stimulation permits such modulation of the target neural structures and, equally importantly, does not require the destruction of nervous tissue. Such electrical stimulation procedures include electroconvulsive therapy (ECT), repetitive transcranial (rTMS) magnetic stimulation and vagal nerve stimulation (VNS).
Efforts have been made to treat psychiatric disorders with peripheral/cranial nerve stimulation. Recently, partial benefits with vagus nerve stimulation in patients with depression have been described in U.S. Pat. No. 5,299,569. Another example of electrical stimulation to treat depression is described in U.S. Pat. No. 5,470,846, which discloses the use of transcranial pulsed magnetic fields to treat depression. Yet further, U.S. Pat. No. 5,263,480 describes that stimulation of the vagus nerve may control depression and compulsive eating disorders and U.S. Pat. No. 5,540,734 teaches stimulation of the trigeminal or glossopharyngeal nerves for psychiatric illness, such as depression.
Deep brain stimulation (DBS) has been applied to the treatment of central pain syndromes and movement disorders, and it is currently being explored as a therapy for epilepsy. For instance, U.S. Pat. No. 6,016,449 and U.S. Pat. No. 6,176,242 disclose a system for the electrical stimulation of areas in the brain for the treatment of certain neurological diseases such as epilepsy, migraine headaches and Parkinson's disease. U.S. Pat. No. 7,313,442 has shown that stimulation of the inferior thalamic peduncle (ITP) or the reticular thalamic nucleus can treat mood and/or anxiety disorders.
Recently, it has been shown that the subgenual gyrus may be stimulated to provide relief to patients suffering from treatment refractory depression (See US Published Applications; 2005/0033379; 20060212091; 2007/0005115; U.S. Pat. No. 7,346,395). However, it is interesting to note that there is considerable asymmetry in the gyrus amongst patients and also across the right and left hemispheres of a single patient. For example, the gyrus may be flatter or more rounded, or multi-lobed or possible only a single gyrus may exist in some patients. Because of this disparately, it is necessary to determine the appropriate location within the subgenual area to stimulate in order to achieve improvement in at least one symptom of the affective disorder. Thus, the present invention is the first to determine the target area within the subgenual area to stimulate to treat a neurological disorder, for example a mood and/or anxiety disorder.